Both the original writing, and the surviving manuscripts, have uncertainty bounds of decades in their dates. The oldest physical pages we still have come from the years 100-200 or so. And assuming that a description of an event can't be written before the event happened (a touchy subject in this case), then the original writing of the Gospels must have been after the start of the First Jewish-Roman War in the year 66. So the gap between the writing and our extant sources could be pretty short, or could be over a century.

https://en.wikipedia.org/wiki/Biblical_manuscript#Earliest_e...

https://en.wikipedia.org/wiki/Gospel#Composition